dolfin team mailing list archive

["Johan Hoffman" <jhoffman@xxxxxxxxxx>]

> On Tue, Feb 19, 2008 at 09:18:54AM +0100, Johan Hoffman wrote:
>> > On Mon, Feb 18, 2008 at 04:35:54PM +0100, Johan Hoffman wrote:
>> >> > This is good juncture at which re-focus on important goals for a
>> >> hopefully not too distant next release. Three priorities that I see
>> are:
>> >> >
>> >> > - New build system.
>> >> >
>> >> > - Improved support for parallel assembly and solve. The class
>> Function
>> >> will probably need the most work. Good goals would be to get Poisson
>> and
>> >> elasticity demos running in parallel.
>> >>
>> >> I thought the Poisson problem was running, and showing good parallel
>> >> scaling? Or maybe that was a test outside the dolfin-dev demos?
>> >
>> > The demo is in src/demo/fem/assembly/.
>>
>> Ok, so the matrix assembly is working and is implemented as a demo, but
>> solve is missing.
>
> Two things are missing: solve and handling forms with coefficients in
> parallel (the Vector in DiscreteFunction holding the dofs should be
> parallel).
>
> Garth has done parallel solve (with PETSc) in
> src/sandbox/passembly/main.cpp
> so it shouldn't be much work to get the solve part going.

Ok.

>> >> We (Nicklas) have now a preliminary distributed parallel
>> implementation
>> >> running for Poisson and a Unicorn flow solver. The structure is still
>> >> quite messy and the partitioning is based on Metis, but we expect it
>> to
>> >> be
>> >> integrated with DOLFIN in the coming months, hopefully before the
>> >> summer.
>> >
>> > Could this be done in small pieces? I'm a little worried about seeing
>> > big changesets that add things to the mesh classes.
>>
>> Yes, we need to figure out how this should be done to best fit with the
>> existing mesh classes. When we have cleaned up the code we will take
>> that
>> discussion here at the dolfin mailing list so that we can agree on a
>> solution.
>
> Excellent.
>
>> >> When the structure is more clear we can discuss on the mailing list
>> how
>> >> to
>> >> best incorporate this into DOLFIN. Apart from the structure of the
>> >> implementation we are also focusing on distributed local mesh
>> >> refinement.
>> >
>> > Great.
>> >
>> > What is the difference from what we have now? Is it the same but with
>> > a distributed mesh (so each processor just sees the local part, not
>> > the whole mesh)? Or is it something different?
>>
>> I think the main issues are to handle refinement over
>> partition-boundaries, and efficient re-partitioning after refinement
>> (for
>> load-balancing).
>
> ok, we haven't considered this at all.
>
>> > I think what we have now can be fairly easily extended to a
>> > distributed mesh without any (significant) changes to the mesh
>> > classes. The key point is to build the DofMap in parallel. Take a look
>> > here, in particular Section 6 and Algorithm 5:
>> >
>> >   http://simula.no/research/scientific/publications/Simula.SC.75
>> >
>>
>> Seems I need a username/password for this.
>
> Sorry, try here:
>
>   http://home.simula.no/~logg/tmp/

Thanks; works better!

/Johan

> --
> Anders
>
>
>> /Johan
>>
>> >> > - Testing of QuadratureFunction and adding corresponding demos.
>> >> >
>> >> > Another point is to add Trilinos as a supported linear algebra back
>> >> end.
>> >> How does this tie up with closer links to PyCC?
>> >> >
>> >> > Garth
>> >>
>> >> - Something else that I think is important is to include geometry in
>> >> DOLFIN. We were to start such a project before Christmas, but we lost
>> >> the
>> >> msc student that was supposed to work on this. I would expect that we
>> >> restart this later this spring. Basically we need to import
>> CAD-geometry
>> >> (or other geometry descriptions), create an internal DOLFIN format
>> >> (typically based on NURBS or similar) with a Geometry-class. Typical
>> >> functionality needed is then to project a point onto the surface
>> >> geometry.
>> >
>> > That would be nice.
>> >
>> >
>> >
>> >> /Johan
>> >>
>> >>
>> >> > _______________________________________________
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>> >> >
>> >>
>> >>
>> >>
>> >>
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>>
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